1.6 g of pyrolusite ore was treted with 50 " mL of " 1.0 N oxalic acid and some sulphuric acid. The oxalic acid left undecomposed was raised to 250 mL in a flask. 25 " mL of " this solution, when titrated with 0.1 N `KMnO_4` required 32 " mL of " this solution. Find out the percentage of pure `MnO_2` and also the percentage of available oxygen from `MnO_2`.
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`25 cm^(3)` of undecomposed oxalic acid required `=32 cm^(3) 0.1N KMnO_(4)` solution Thus, `250 cm^(3)` of undecomposed oxalic acid required `=320cm^(3) 0.1N KMnO_(4)` solution `-=32 cm^(3) 1N KMnO_(4)` solution `=32 cm^(3) 1N` oxalic acid solution Oxalic acid used by pyrolusite `=(50-32) cm^(3) 1 N` solution `=18cm^(3) 1N` solution `-=18 cm^(3) 1 N MnO_(2)` solution Mass of `MnO_(2)=(NxxExxV)/(1000)=(1xx18xx87)/(1000xx2)=0.783 g` Percentage of `MnO_(2)=(0.783)/(1.6)xx100=48.9` `underset(87g)(MnO_(2))to MnO+underset(16 g)(O)` Oxygen given by 0.783 g `MnO_(2)=(16)/(87)xx0.783=0.144 g` % of available oxygen`= (0.144)/(1.6)xx100=9.0`
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